Controlled‐Release Fertilizer: A Review on Biopolymers‐Based Composite, Fabrication, and Application

Controlled‐release fertilizers (CRFs) offer a sustainable pathway to enhance nutrient use efficiency while reducing the environmental burdens associated with conventional fertilizers. By delivering nutrients in synchrony with plant demand, CRFs minimize volatilization, leaching, and eutrophication and support soil microbial function. Biopolymer‐based matrices have emerged as promising candidates due to their biodegradability and tunable properties, yet their low mechanical strength and high permeability require reinforcement and improved processing strategies. Advances in coating technologies, ranging from chemical to solvent‐free physical methods, have been key to improving CRF performance. Although chemical coatings are effective, their reliance on organic solvents motivates a shift toward greener techniques such as melt blending, spray coating, and extrusion. Melt blending is particularly attractive for its simplicity and compatibility with three‐dimensional (3D) printing, enabling precise control of architecture and release kinetics. Remaining challenges include optimizing material formulations and tailoring release profiles to specific crops and environments.